Optimized multifocal wavefronts for presbyopia correction

ABSTRACT

Example embodiments include methods for forming a subsurface optical structure in an ophthalmic lens. The method may include defining a phase-wrapped wavefront for causing the ophthalmic lens to diffract light to multiple focal points; defining a spherical wavefront configured for inducing a spherical aberration in the ophthalmic lens; and generating, based on the wavefronts, energy output parameters for forming a subsurface optical structure in the ophthalmic lens using an energy source, wherein the subsurface optical structure is configured to correct presbyopia by providing extended depth of focus that produces increased intermediate vision quality. Also disclosed are ophthalmic lenses with Fresnel rings that effect a phase-wrapped wavefront with a spherical aberration.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/049,277, filed Jul. 8, 2020, which is herein incorporated byreference in its entirety and for all purposes.

BACKGROUND

Optical aberrations that degrade visual acuity are common. Opticalaberrations are imperfections of the eye that degrade focusing of lightonto the retina. Common optical aberrations include lower-orderaberrations (e.g., astigmatism, positive defocus (myopia) and negativedefocus (hyperopia)) and higher-order aberrations (e.g., sphericalaberrations, coma and trefoil).

Existing treatment options for correcting optical aberrations includeglasses, contact lenses, and reshaping of the cornea via laser eyesurgery. Additionally, intraocular lenses are often implanted to replacenative lenses removed during cataract surgery.

Presbyopia may be defined as a gradual loss of near vision, or theability to focus on nearby objects, that may occur naturally with age.Presbyopia may become noticeable for patients in their early to mid-40sand may continue to worsen over time as they age until around age 65. Aspatients age, the crystalline lens gradually stiffens and grows in size,generally making it difficult for the lens to accommodate (or changeshape) adequately to focus on nearby objects.

BRIEF SUMMARY

The following presents a simplified summary of some embodiments of theinvention in order to provide a basic understanding of the invention.This summary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome embodiments of the invention in a simplified form as a prelude tothe more detailed description that is presented later.

Embodiments described herein are directed to ophthalmic lenses having atleast one subsurface optical structure (e.g., diffractive opticalstructures and/or non-diffractive optical structures) with enhanceddistribution of refractive index values. In many embodiments, thesubsurface refractive index variations are formed via focusingfemtosecond duration laser pulses onto a targeted sequence of subsurfacevolumes of an ophthalmic lens. The refractive indexes of the annularoptical structure vary radially relative to the optical axis up to anupper limit refractive index (e.g., providing any suitable phase changeless than 1.0 wave). The refractive indexes of the annular opticalstructure are equal to the upper limit refractive index over a range ofradii (e.g., at least 0.15 mm length) from the optical axis. In manyembodiments, the refractive indexes of the annular optical structure areequal to a lower limit refractive index (e.g., providing a phase changeof 0.0 waves) over a range of radii (e.g., at least 0.15 mm length) fromthe optical axis. The enhanced distribution of refractive index valuescan be formed using fewer laser pulses in comparison with acorresponding distribution of refractive index values determined via aratio approach. Additionally, limiting the refractive index values toequal to or less than the upper limit refractive index helps to reducedamage induced by the sequence of laser pulses at a given pulse energylevel as compared to forming a corresponding subsurface opticalstructure(s) using refractive index values that are greater than theupper limit refractive index. The approaches described herein may beuseful in forming a subsurface optical structure(s) in any suitableophthalmic lenses (e.g., intraocular lenses, contact lenses, corneas,glasses, and/or native lenses).

In some embodiments, methods, systems, and devices are described fordetermining parameters for forming an optical structure (e.g., asubsurface optical structure) in an ophthalmic lens for improving visionin a patient. These parameters may be used to control an energy sourceto appropriately form the desired optical structure.

In many cases, presbyopia patients less than 45 years old may beclassified as early presbyopes requiring relatively minor correction;presbyopia patients between 45 and 55 years old may be classified as midpresbyopes requiring a moderate level of correction; and presbyopiapatients over the age of 55 years old (or patients who have received anon-accommodating manner focal intraocular lens (IOL)) may be classifiedas advanced presbyopes requiring a relatively large level of correction.

Disclosed herein are methods for forming subsurface optical structuresin an ophthalmic lens for improving patient vision (e.g., for correctingpresbyopia). In some embodiments, the method includes defining a firstphase-wrapped wavefront corresponding to a first optical structureconfigured to cause the ophthalmic lens to diffract light to multiplefocal points, wherein the first phase-wrapped wavefront is a wavefronthaving a first predetermined phase height (e.g., not equal to 1 wave);defining a first spherical wavefront configured for inducing a firstspherical aberration in the ophthalmic lens; and generating, based onthe first phase-wrapped wavefront and the first spherical wavefront,energy output parameters for forming a first subsurface opticalstructure in the ophthalmic lens using an energy source, wherein thefirst subsurface optical structure is configured to correct presbyopiaby providing extended depth of focus that produces increasedintermediate vision quality.

In some embodiments, the method may include accessing an opticalprescription for the patient, wherein the optical prescription comprisesone or more prescription parameters for refracting light directed at aretina of the patient so as to improve vision; and generating a firstvariable wavefront based on the optical prescription, wherein the firstvariable wavefront comprises at least one portion that has a phaseheight greater than 1 wave; wherein generating the first phase-wrappedwavefront comprises collapsing the first variable wavefront to the firstpredetermined phase height.

In some embodiments, the energy output parameters specify a plurality ofpower levels corresponding to a plurality of optical zones on theophthalmic lens. The method may include directing a first energy beamfrom the energy source at a first subsurface optical zone of theophthalmic lens for a first duration, wherein a power level of the firstenergy beam is based on a corresponding power level as specified by theenergy output parameters; and directing a second energy beam from theenergy source at a second subsurface optical zone on the ophthalmic lensfor a second duration, wherein a power level of the second energy beamis based on a corresponding power level as specified by the energyoutput parameters. The first energy beam and the second energy beam mayalter refractive indexes of the first subsurface optical zone and thesecond subsurface optical zone, respectively, and wherein the firstsubsurface optical structure comprises the first subsurface optical zoneand the second subsurface optical zone.

In some embodiments, the first optical structure is configured to causethe ophthalmic lens to be a bifocal lens having a 2 diopter add power.In some embodiments, the first optical structure is configured to causethe ophthalmic lens to be a bifocal lens having a 1.5 diopter add power.In some embodiments, the first predetermined phase height is betweenabout 0.5 to 0.6 waves. In some embodiments, the first sphericalaberration is around −0.2 μm. In some embodiments, the first sphericalaberration is around 0.2 μm.

In some embodiments, forming the subsurface optical structure comprisesdirecting an energy beam toward a volume of the ophthalmic lens so as tochange a refractive index of the volume.

In some embodiments, the method may include defining a secondphase-wrapped wavefront corresponds to a second optical structureconfigured to cause the ophthalmic lens to diffract light to multiplefocal points, wherein the second phase-wrapped wavefront is a wavefronthaving a second predetermined phase height (e.g., not equal to 1 wave);defining a second spherical wavefront configured to cause a secondspherical aberration in the ophthalmic lens; and generating, based onthe second phase-wrapped wavefront and the second spherical wavefront,energy output parameters for forming a second subsurface opticalstructure in the ophthalmic lens using an energy source. In someembodiments, the first subsurface optical structure is configured tocorrect a first stage of presbyopia in the patient, the secondsubsurface optical structure is configured to correct a second stage ofpresbyopia in the patient, and the second stage of presbyopia in thepatient is later than the first stage of presbyopia in the patient.

Also disclosed are of ophthalmic lenses for improving vision (e.g., forcorrecting presbyopia in a patient), which may in some embodiments beperformed using the described methods. In some embodiments an ophthalmiclens may include a first subsurface optical structure comprisingconcentric Fresnel rings within an interior of the ophthalmic lens. Eachof the concentric Fresnel rings can define a volume having a desiredrefractive index. The first subsurface optical structure may beconfigured to: induce a first spherical aberration in the ophthalmiclens; and diffract light to multiple focal points based on aphase-wrapped wavefront having a first predetermined phase height (e.g.,not equal to 1 wave).

In some embodiments, the ophthalmic lens is an intraocular lens, acontact lens, or a cornea of the patient. In some embodiments, whereinthe first subsurface optical structure is configured to cause theophthalmic lens to be a bifocal lens having a 2 diopter add power. Insome embodiments, the first subsurface optical structure is configuredto cause the ophthalmic lens to be a bifocal lens having a 1.5 diopteradd power. In some embodiments, the first predetermined phase height isbetween about 0.5 to 0.6 waves. In some embodiments, the first sphericalaberration is around −0.2 μm. In some embodiments, the first sphericalaberration is around 0.2 μm

In some embodiments, the ophthalmic lens includes a second subsurfaceoptical structure. The first subsurface optical structure can beembedded in a first layer of the ophthalmic lens. The second subsurfaceoptical structure can be embedded in a second layer of the ophthalmiclens. In some embodiments, the first subsurface optical structure isconfigured to correct a first stage of presbyopia in the patient and thesecond subsurface optical structure is configured to correct a secondstage of presbyopia in the patient. The second stage of presbyopia inthe patient can be later than the first stage of presbyopia in thepatient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustration of an ophthalmic lens that includessubsurface optical structures with enhanced distribution of refractiveindex variations, in accordance with embodiments.

FIG. 2 is a plan view illustration of a layer of the subsurface opticalstructures of the ophthalmic lens of FIG. 1 .

FIGS. 3A-3B illustrate example wavefronts through a medium for paralleland converging rays of light.

FIGS. 3C-3D illustrate example wavefronts that may simulate aberrationsof the eye.

FIG. 3E illustrates a two-dimensional wavefront map and a correspondingfirst variable wavefront.

FIG. 3F illustrates a first phase-wrapped wavefront corresponding to thefirst variable wavefront.

FIG. 4 illustrates a second phase-wrapped wavefront having a phaseheight less than 1 wave.

FIG. 5 illustrates a two-dimensional map representation of aphase-wrapped wavefront phase-wrapped at an optical phase height lessthan 1 wave, such as the wavefront in FIG. 4 .

FIG. 6 illustrates an example of an optical structure having diffractiveproperties.

FIG. 7 is a graph illustrating the relative distribution of lightbetween a near-vision focal point and a far-vision focal point as phaseheight of a wavefront is adjusted between 0 wave and 1 wave.

FIG. 8 illustrates a cross section of an ophthalmic lens including asubsurface optical structure having multiple substructures.

FIGS. 9A-9B illustrate example conceptualizations of an ophthalmic lenshaving a plurality of optical zones.

FIG. 10 illustrates an example method for determining parameters forforming a subsurface optical structure for improving vision in apatient.

FIG. 11 illustrates an example of presbyopia progression in a patient.

FIG. 12 illustrates an example chart of presbyopia progression.

FIG. 13 illustrates example image quality metrics across a diopter rangeusing a number of bifocal wavefronts.

FIG. 14 illustrates the concept of spherical aberrations in lenses.

FIG. 15 illustrates example image quality metrics for a patient withpresbyopia with lenses having positive and negative sphericalaberrations as compared to a control with zero spherical aberration.

FIG. 16 illustrates a graph overlaying the line for a 2-diopter bifocalof FIG. 13 with the spherical aberration lines, and the control line ofFIG. 15 .

FIG. 17 illustrates the graph of FIG. 16 further overlaying linescorresponding to image quality metrics of phase-wrapped trifocals.

FIG. 18 illustrates a graph including a number of the previouslydescribed lines as well as lines corresponding to bifocals withspherical aberrations.

FIGS. 19A-19B illustrate cross-sections of the wavefronts correspondingto particular lines of FIG. 18 .

FIG. 20 is a table showing example wavefronts that may be implementedfor different stages of presbyopia.

FIG. 21 illustrates an example method 2000 for forming a subsurfaceoptical structure in an ophthalmic lens for correcting presbyopia in apatient.

FIG. 22 illustrates simulated resulting phase-wrapped wavefronts for adesign 0.4 wave height phase-wrapped wavefront due to practicallimitations associated with inducing the design 0.4 wave heightphase-wrapped wavefront in an artificial or biological optical material.

FIG. 23 illustrates simulated resulting through-focus retinal imagequality for the simulated resulting phase-wrapped wavefronts of FIG. 22.

FIG. 24 illustrates simulated resulting phase-wrapped wavefronts for ascaled-up version of the 0.4 wave height phase-wrapped wavefront of FIG.22 .

FIG. 25 illustrates simulated resulting through-focus retinal imagequality for the simulated resulting phase-wrapped wavefronts of FIG. 24.

FIG. 26 shows simulated resulting through-focus retinal image qualitiesillustrating that near visual benefit can be recovered by scaling adesign wavefront height.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention may be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

FIG. 1 is a plan view illustration of an ophthalmic lens 10 thatincludes one or more subsurface optical structures 12 with annulardistribution of refractive index variations, in accordance withembodiments. The one or more subsurface structures 12 described hereincan be formed in any suitable type of ophthalmic lens including, but notlimited to, intra-ocular lenses, contact lenses, corneas, spectaclelenses, and native lenses (e.g., a human native lens). The one or moresubsurface optical structures 12 with annular distribution of refractiveindex variations can be configured to provide a suitable refractivecorrection for each of many optical aberrations such as astigmatism,myopia, hyperopia, spherical aberrations, coma and trefoil, as well asany suitable combination thereof

FIG. 2 is a plan view illustration of one of the subsurface opticalstructures 12 of the ophthalmic lens 10. The illustrated subsurfaceoptical structure 12 includes concentric circular sub-structures 14separated by intervening line spaces or gaps 16. In FIG. 2 , the size ofthe intervening line spaces 16 is shown much larger than in many actualembodiments. For example, example embodiments described herein have anouter diameter of the concentric circular sub-structures 14 of 3.75 mmand intervening line spaces 16 of 0.25 um, thereby having 1,875 of theconcentric circular sub-structures 14 in embodiments where theconcentric circular substructures 14 extend to the center of thesubsurface optical structure 12. Each of the concentric circularsub-structures 14 can be formed by focusing suitable laser pulses ontocontiguous sub-volumes of the ophthalmic lens 10 so as to induce changesin refractive index of the sub-volumes so that each of the sub-volumeshas a respective refractive index different from an adjacent portion ofthe ophthalmic lens 10 that surrounds the sub-structure 14 and is notpart of any of the subsurface optical structures 12.

In many embodiments, a refractive index change is defined for eachsub-volume of the ophthalmic lens 10 that form the subsurface opticalstructures 12 so that the resulting subsurface optical structures 12would provide a desired optical correction when formed within theophthalmic lens 10. The defined refractive index changes are then usedto determine parameters (e.g., laser pulse power (mW), laser pulse width(fs)) of laser pulses that are focused onto the respective sub-volumesto induce the desired refractive index changes in the sub-volumes of theophthalmic lens 10.

While the sub-structures 14 of the subsurface optical structures 12 havea circular shape in the illustrated embodiment, the sub-structures 14can have any suitable shape and distribution of refractive indexvariations. For example, a single sub-structure 14 having an overlappingspiral shape can be employed. In general, one or more substructures 14having any suitable shapes can be distributed with intervening spaces soas to provide a desired diffraction of light incident on the subsurfaceoptical structure 12 ss. More information about subsurface opticalstructures and forming such structures may be found in U.S. ProvisionalApplication No. 63/001,993, which is incorporated herein by reference inits entirety for all purposes.

In some embodiments, a system including one or more processors may beconfigured to determine parameters for forming one or more opticalstructures (e.g., subsurface optical structures) for improving orcorrecting vision. In some embodiments, the one or more processors ofthe system may be configured to access a first optical prescription forthe patient. The first optical prescription may be prescribed by, forexample, an optometrist. The first optical prescription may include oneor more prescription parameters for refracting light directed at aretina of the patient so as to improve vision. The prescriptionparameters may be determined based on any suitable means of measurement.The prescription parameters may specify any suitable parameters forcorrecting or improving vision. For example, the prescription parametersmay include diopter values of sphere, cylinder, or axis. Theprescription parameters may include parameters for correcting one ormore of a variety of low-order aberrations (e.g., myopia, hyperopia,astigmatism) and high-order aberrations (e.g., spherical aberration,coma, trefoil).

FIGS. 3A-3B illustrate example wavefronts 305, 306 through a medium forparallel and converging rays of light. Prescriptions for correcting orimproving vision of a patient can essentially be described as aprescription for creating an optical structure that effects a wavefrontconfigured to modify incoming rays of light before they reach the retinaof the patient. A wavefront is an imaginary surface of constant phase. Awavefront can also be thought of as a surface that is normal orperpendicular to rays of light passing through the wavefront. FIG. 3Aillustrates a planar wavefront 305 from parallel rays of light. As isevident, the wavefront 305 is perpendicular to the parallel rays oflight at each point of intersection. FIG. 3B illustrates a sphericalwavefront 306 from converging rays of light. FIG. 3B simulates an idealconfiguration of an eye, where the rays of light converge at a singlepoint (on the retina 302). Each of the rays is perpendicular to thewavefront 307 at its respective point of intersection with the wavefront307. The illustrated rays converge at a single point.

FIGS. 3C-3D illustrate example wavefronts 308, 309 that may simulateaberrations of the eye. Unlike the rays in FIG. 3B, the rays in FIG. 3Cdo not converge at a single point on the retina 302 (e.g., at or nearthe macula). Such non-convergence may cause issues with vision by notallowing for a focused image (e.g., causing myopia). FIG. 3D illustratesan aberrated wavefront 309 simulating another aberration of the eye(e.g. higher order aberrations). Again, each of the rays isperpendicular to the wavefront 309 at its respective point ofintersection with the wavefront 309. And again, as illustrated, the raysin FIG. 3D do not converge at a single point on the retina 302 (and infact do not converge at all), causing issues with vision. An appropriateoptical structure with a corrective wavefront may be used to correctissues produced by aberrations by, for example, refracting light suchthat the light rays are made to converge at a single appropriate pointon the retina 302. Disclosed herein are methods, devices, and systemsfor use in forming such optical structures. Although the disclosurefocuses on methods, devices, and systems for correcting aberrations ofthe eye, the disclosure also contemplates enhancing what may beconsidered normal vision by similar methods, devices, and systems.

FIG. 3E illustrates a two-dimensional wavefront map 310 and acorresponding first variable wavefront 320. In some embodiments, the oneor more processors may use the first optical prescription to determine awavefront for an optical structure for correcting or improving vision ofthe patient. In some embodiments, the one or more processors maygenerate a wavefront map, which may be visualized, for example, by thetwo-dimensional wavefront map 310. The contours of the two-dimensionalwavefront map 310 may specify different optical phases of thecorresponding wavefront. For example, the different shades in thetwo-dimensional wavefront map 310 specifies different optical phases ofthe corresponding wavefront. In some embodiments, the one or moreprocessors may do so by first computing the Zernike coefficient fordefocus (C_(2,0)) using the following equation:C _(2,0) =P*r _(max) ²/(4*sqrt (3)),   (1)where P is an add power specified in the first prescription, and r_(max)is the maximum radius of an optical zone.The Zernike coefficient is a scalar that may be expressed in units ofmicrometers. In some embodiments, the two-dimensional wavefront map maythen be calculated using the following equation:W _(um) =C _(2,0)*sqrt(3)*(2*ρ²−1),   (2)where ρ is a normalized radial pupil coordinate (radialcoordinate/r_(max)) W_(um) provides a value (e.g., in units ofmicrometers) for each point of a two-dimensional wavefront map.Referencing FIG. 3D, the two-dimensional wavefront map 310 for aparticular optical prescription may be generated using this equation.

In some embodiments, the one or more processors may be configured togenerate a first variable wavefront based on the first opticalprescription. Referencing FIG. 3D, for example, the first variablewavefront 320 may be generated based on specifications provided by thefirst optical prescription. The first variable wavefront describes awavefront in units of waves with respect to a specified wavelength. Insome embodiments, the first variable wavefront comprises at least oneportion that has a phase height greater than 1 wave. In someembodiments, the first variable wavefront may be generated based on thetwo-dimensional wavefront map. The first variable wavefront may bedetermined with respect to any desired wavelength by dividing W_(um) foreach point by the desired wavelength. For example, the first variablewavefront may be determined with respect to a center of the visiblespectrum (e.g., 0.555 μm in daylight). In this example, the equationbelow may be used to generate a first variable wavefront at 0.555 μm).W _(wv) =W _(um)/0.555 μm   (3)

FIG. 3F illustrates a first phase-wrapped wavefront 325 corresponding tothe first variable wavefront 320. In some embodiments, the one or moreprocessors may be configured to phase wrap the first variable wavefront,which may include collapsing the first variable wavefront to generate afirst phase-wrapped wavefront. Phase wrapping the first variablewavefront may involve collapsing the first variable wavefront into awavefront having a predetermined phase height (i.e., the height frompeak to valley of the wavefront). For example, referencing FIG. 3B, thefirst phase-wrapped wavefront 325 may have a phase height of 1 wave.Phase-wrapping a variable wavefront to 1 wave causes no appreciablechange in diffraction or refraction of light rays, and may thus besuitable, for example, for a patient having only myopia. An exampleMatlab algorithm for phase-wrapping to a phase height of 1 wave is shownbelow, where W555=W_(wv) and Wrap=1:

while cnt == 0 W555( W555 < −Wrap ) = W555( W555 < −Wrap ) + Wrap; ifsum( W555(:) < −Wrap ) == 0 cnt = 1; end end cnt = 0; while cnt == 0W555( W555 > Wrap ) = W555( W555 > Wrap ) − Wrap; if sum( W555(:) > Wrap) == 0 cnt = 1; end end

In some embodiments, collapsing the rust variable wavefront may includeidentifying a plurality of discrete segments of the first variablewavefront. In some embodiments, as is the case in FIG. 3F, each of thesediscrete segments (e.g., 320-1 to 320-n) may be circumferential discretesegments that extend radially around the two-dimensional wavefront map310 of the ophthalmic lens. For example, the discrete segment 320-1 inthe first variable wavefront 320 may correspond to the portion 310-1 inthe two-dimensional wavefront 310, the discrete segment 320-2 maycorrespond to the segment 310-2, the discrete segment 320-3 maycorrespond to the segment 310-3, and so on. In other embodiments, thediscrete segments may not be circumferential, and the first variablewavefront may be segmented based on, for example, phase height. In theexample illustrated in FIG. 3F, each of the discrete segments (325-1 to325-n) is circumferential, and each discrete segment is adjacent to andconcentric with another discrete segment. For example, the discretesegment 325-2 is adjacent to and concentric with the discrete segment325-1 (similarly, the discrete segment 325-3 is adjacent to andconcentric with the discrete segment 325-2, and so on). In someembodiments, the one or more processors of the system may reduce a phaseheight of each discrete segment by a respective scalar such that a peakof the first discrete segment is at a desired phase height. For example,in FIG. 3F, the phase height of each discrete segment is reduced to apredetermined phase height of 1 wave, yielding the first phase-wrappedwavefront 325. As mentioned above, collapsing the first variablewavefront 320 to the phase-wrapped wavefront 325 (which is collapsed to1 wave) causes no appreciable change in diffraction or refraction, andlight rays passing an optical structure based on the collapsedphase-wrapped wavefront 325 essentially behave in the same manner aslight rays passing an optical structure formed based on the firstvariable wavefront 320. The resulting phase-wrapped wavefront mayinclude a central discrete segment (e.g., the discrete segment 325-1)and a number of surrounding circumferential, adjacent echelettes (e.g.,the discrete segments 325-2 to 325-n) as illustrated in FIG. 3E.

FIG. 4 illustrates a second phase-wrapped wavefront 427 having a phaseheight less than 1 wave. In some embodiments, the system may beconfigured to phase wrap the first variable wavefront at a predeterminedphase height that is not at 1 wave to generate a second phase-wrappedwavefront. For example, referencing FIG. 5 , the predetermined phaseheight of the illustrated phase-wrapped wavefront 427 is less than 1wave. As discussed further below, collapsing a wavefront to a phaseheight other than 1 wave causes diffraction, which may be useful forcreating a multifocal optical structure. Thus, such a wavefront may bereferred to herein as a “diffractive phase-wrapped wavefront.” In someembodiments, the phase-wrapped wavefront may be collapsed at a phaseheight greater than 1 wave. The decision as to whether a wavefront iscollapsed to a phase height greater than 1 wave or to a phase heightless than 1 wave may have some practical effects. For example, phasewrapping at greater than 1 wave may reduce diffractive chromaticeffects. However, phase wrapping to greater than 1 wave requires moreavailable refractive index change as compared to phase wrapping to lessthan 1 wave, and any material used is subject to a given range ofpossible refractive index changes, which may be a limiting factor (e.g.,limited by the properties of the material). This may be ultimatelyovercome in many cases by writing multiple layers or volume filling,however, but there are still limits. So there is a tradeoff betweenphase wrapping at greater than 1 wave or less than 1 wave. Whether awave front is phase-wrapped to less than 1 wave or greater than 1 wavemay also have implications for energy distribution of far/near vision(e.g., for patients with presbyopia), and the practitioner can controlthis as necessary to achieve a desired effect.

FIG. 5 illustrates a two-dimensional map representation of aphase-wrapped wavefront 500 phase-wrapped at an optical phase heightless than 1 wave, such as the wavefront 427 in FIG. 4 . The illustratedphase-wrapped wavefront has a 3.0 mm diameter optical zone and adiffractive bifocal with 2.5 Diopters (D) of add-power. The diffractivebifocal wavefront is designed to have an optical phase height of 0.35waves at 555 nm wavelength. As illustrated, the phase-wrapped wavefront500 includes five discrete circumferential segments, each segmentgradually decreasing in phase height (from 0.35 waves to 0 waves) froman inner boundary of the segment to an outer boundary of the segment.

FIG. 6 illustrates an example of an optical structure 610 havingdiffractive properties. In some embodiments, an optical structure havinga phase-wrapped wavefront collapsed at a phase height other than 1 wave(e.g., less than 1 wave) has diffractive effects that create multiplefocal points, which may be useful, for example, in correcting vision inpatients having presbyopia. As illustrated in FIG. 6 , light rayspassing through the optical structure 610, which is an optical structurewith diffractive properties, an incident beam can be focusedsimultaneously at several positions along the propagation axis.Diffraction in this manner can be used to create multiple focal points,for example, to improve the vision of patients with presbyopia. Forexample, an optical structure having diffractive properties may have afirst focal point for near-vision and a second focal point forfar-vision.

FIG. 7 is a graph 700 illustrating the relative distribution of lightbetween a near-vision focal point and a far-vision focal point as phaseheight of a wavefront is adjusted between 0 wave and 1 wave. In someembodiments, the system may generate diffractive phase-wrappedwavefronts (e.g., phase-wrapped wavefronts at less than 1 wave orgreater than 1 wave), for conditions such as presbyopia that aredesigned to provide both high optical quality for far-vision andintermediate- and near-vision (e.g., good through-focus image quality),but with the understanding that there may be a trade-off. An examplerepresentation of this trade-off is illustrated in FIG. 7 . Asillustrated by the far-vision curve 710, as the phase height increasesto 1 wave, the percentage of light distributed to the far-vision focalpoint by the diffraction of incoming light decreases (and thereforeimage quality for far-vision generally decreases). By contrast,referencing the near-vision curve 720, as the phase height increases to1 wave, the percentage of light distributed to the near-vision focalpoint increases (and therefore image quality for near-vision generallyincreases). In some embodiments, a desired distribution for thistradeoff may be specified in an optical prescription (e.g., as addpower), and may be determined based on any suitable of patient-dependentfactors. For example, the patient who often engages in high-detail work(e.g., a watchmaker) may require a relatively high add power (e.g., 4.0diopters). A relatively low add power (e.g., 1.0 diopters) may besuitable for a patient who does not engage in such high-detail work. Adiffractive phase-wrapped wavefront may be generated with a prescriptionhaving such considerations in mind to come to a desired trade-off.

In some embodiments, the one or more processors may be configured togenerate multiple wavefronts, for example, to correct multipleaberrations of the eye. In some embodiments, the one or more processorsmay generate a second variable wavefront based on a second opticalprescription, wherein the second optical prescription comprises an addpower for multifocal vision correction. The term second opticalprescription does not necessarily reference a separate prescription, andmay instead refer to separate one or more parameters for correcting adifferent aberration than the first optical prescription. For example, apatient may receive a single prescription from an optometrist forcorrecting near-vision based on parameters of a first opticalprescription and for correcting far-vision based on parameters of asecond optical prescription (e.g., including an add power). In someembodiments, the one or processors may phase-wrap the second variablewavefront, wherein phase wrapping the second variable wavefrontcomprises collapsing the second variable wavefront to a secondphase-wrapped wavefront having a second predetermined phase height. Thesecond predetermined phase height may be less than 1 wave, so as toallow for diffractive effects as discussed above. In some embodiments, afirst phase-wrapped wavefront may have a phase height of 1 wave, and thesecond phase-wrapped wavefront may have phase height less than 1 wave.In these embodiments, the first phase-wrapped wavefront may be usefulfor correcting myopia and the second phase-wrapped wavefront may beuseful for correcting presbyopia, for example.

FIG. 8 illustrates a cross section of an ophthalmic lens including asubsurface optical structure having multiple substructures 810. In someembodiments, the one or more processors may be configured to generate,based on the first phase-wrapped wavefront, energy output parameters forforming a first optical structure using an energy source. In someembodiments, the first optical structure may be configured to refractlight directed at the retina of the patient so as to improve vision. Insome embodiments, the optical structure may be a subsurface opticalstructure. For example, referencing the cross-section illustrated inFIG. 8 , the optical structure may be a subsurface optical structurehaving multiple substructures 810 that may be concentric. As discussedin further detail above, subsurface optical structures may be achievedby focusing laser pulses appropriately to depths within the ophthalmiclens such that changes in refractive property occur to sub-volumes inthe interior of the ophthalmic lens.

The conventional approach for forming a diffractive ophthalmic lensinvolves creating Fresnel rings that project outward from an exteriorsurface of the ophthalmic lens. Such a configuration not only increasesthe thickness profile of the lens, but it may also cause issues with theoptical properties of the ophthalmic lens. For example, in the case of acontact lens, disposing Fresnel rings on the outward-facing exteriorsurface of the contact lens may cause errors in light diffraction orrefraction because the level of tear film may vary across the peaks andvalleys of the Fresnel rings. And disposing the Fresnel rings on theinward-facing exterior surface of the contact lens may cause patientdiscomfort. Additionally, rings disposed on an exterior surface of theophthalmic lens may become sites for the accumulation of debris whichcauses light scatter and loss of contrast.

Moreover, conventional approaches rely on changes in the thickness ofophthalmic lenses to supply the base power of the ophthalmic lenses. Inthese approaches, the refractive index of the material throughout anophthalmic lens may remain constant. This reliance on thicknessnecessarily means that lenses with relatively high base powers arerelatively thick. For contact lenses, this may mean patient discomfort.For IOLs, this may mean an increase in patient risk during surgery, anda higher potential for complications (e.g., because it may be moredifficult to get the IOL seated in the capsular bag). By contrast, thedisclosed methods of creating subsurface optical structures using anenergy system (e.g., a laser) does not rely on changing the thickness ofan ophthalmic lens for the base power. Rather, as explained above,refractive indices of subvolumes within the ophthalmic lens are modifiedto supply the base power of the ophthalmic lens and thereby refractand/or diffract light as desired. Finally the use of an energy system asdescribed below with respect to optical zones provides increasedresolution as compared to more conventional techniques such ascryolathes or molded injection.

FIGS. 9A-9B illustrate example conceptualizations of an ophthalmic lens900 having a plurality of optical zones. In some embodiments, anophthalmic lens may be divided up into a plurality of pixels, each pixelcorresponding to an optical zone. An optical zone may be a sub-region ora sub-volume of an ophthalmic lens. This is illustrated in FIG. 9A,which shows the ophthalmic lens 900 divided up into a plurality ofpixels (e.g., the pixels 910 and 920) in a grid fashion. Although FIG.9A illustrates uniform pixels that are square shaped, this disclosurecontemplates that pixels may be of any suitable shape (e.g., hexagonal,pentagonal, circular) and that they may not be uniform (e.g., they mayof different shapes and sizes). A pixel area may correspond to theresolution of an energy delivery system (e.g., a laser system)configured to form an optical structure corresponding to a phase-wrappedwavefront. That is, a pixel area may correspond to a minimum area of asub-region of the ophthalmic lens at which the energy delivery systemmay focus an energy beam (e.g., a laser pulse) to change a refractiveindex of the sub-volume associated with the sub-region. FIG. 9Billustrates another conceptualization of optical zones, where theophthalmic lens is not divided up into discrete pixels. Instead, theophthalmic lens is mapped out using a coordinate system (e.g., atwo-dimensional x-y coordinate system, a three-dimensional x-y-zcoordinate system, or a polar coordinate system (radius and angle)). Forexample, the points 912 and 922 may each have a respective coordinate inthe coordinate system.

In some embodiments, the generated energy output parameters may specifyan amount of power that is to be delivered by the energy delivery systemat one or more optical zones. For example, referencing FIG. 9A, theenergy output parameters may specify power levels (e.g., in Watts) forone or more laser pulses that are to be delivered by a laser system atthe pixel 910 and the pixel 920. Similarly, referencing FIG. 9B, theenergy output parameters may specify power levels for a plurality ofcoordinates associated with the ophthalmic lens (e.g., the points 912and 922). In some embodiments, the generated energy output parametersmay specify a duration during which energy beam may be directed at oneor more optical zones. For example, the energy output parameters mayspecify pulse durations for directing a laser beam at one or more of theoptical zones. In some embodiments, the energy output parameters mayspecify a depth at which energy beam is to be delivered in forming anoptical structure. For example, the energy output parameters may specifythat a first set of pulses is to be delivered to a set of optical zonesat a first depth along a first layer of the ophthalmic lens, and mayfurther specify that a second set of pulses is to be delivered to asecond set of optical zones at a second depth along a second layer ofthe ophthalmic lens. In this example, the first layer may be based on aphase-wrapped wavefront collapsed at 1 wave (e.g., for correctingmyopia), and the second layer may be based on a phase-wrapped wavefrontcollapsed at less than 1 wave (e.g., for correcting presbyopia). Thefirst set of pulses in this example may be associated with a first setof energy output parameters (e.g., power levels, pulse durations,depths) for a plurality of optical zones, and the second set of pulsesin this example may be associated with a second set of energy outputparameters.

In some embodiments, the one or more processors, and generating theenergy output parameters, may apply a calibration function so as tocreate a tailored set of parameters for real-world conditions. Thecalibration function may depend on any suitable factors. For example,the one or more processors may apply a calibration function based on oneor more of a material property of the ophthalmic lens, a gender of thepatient, an age of the patient, a depth at which an optical structure(e.g., a subsurface optical structure) is to be formed in the ophthalmiclens, a number of layers, the distance by which different layers areseparated, and/or properties of an energy source for which the energyoutput parameters are generated (e.g., scan speed, numerical aperture,wavelength, pulse width, repetition rate, writing depth, line-spacing,scan architecture).

In some embodiments, the one or more processors may be configured togenerate energy output parameters for forming multiple opticalstructures. For example, the one or more processors may generate energyoutput parameters for forming a first subsurface optical structure basedon a first phase-wrapped wavefront having a phase height of 1 wave(e.g., for correcting myopia) and a second subsurface optical structurebased on a second phase-wrapped wavefront having a phase height lessthan 1 wave so as to diffract light (e.g., for correcting presbyopia).In these embodiments, what results may be a multifocal ophthalmic lensconfigured to create multiple focal points within the eye. In someembodiments, these optical structures may be formed as distinct layers(e.g., in a cornea, a contact lens, an intraocular lens). In otherembodiments, the one or more processors may generate parameters forforming a single optical structure as a single layer that combines thefirst phase-wrapped wavefront and the second phase-wrapped wavefrontsuch that the single layer has the effects specified by the twowavefronts.

In some embodiments, the system may further include an energy sourceconfigured to direct one or more energy beams toward the opticalstructure so as to form the first optical structure based on the energyoutput parameters. In other embodiments, the system may not include suchan energy source, and may simply send the energy output parameters to adifferent system that includes an energy source for forming opticalstructures. In some embodiments, the energy source may be a laser sourceconfigured to deliver targeted pulsed or continuous-wave laser beams.

Although the examples in the disclosure focus on correction of standardsphere/cylinder error and/or presbyopia, the disclosure contemplates thegeneration of wavefronts that may be used to form optical structures forcorrecting any suitable aberration (e.g., customized higher orderaberrations, myopia progression peripheral error). For example,wavefronts described by any combination of Zernike polynomials may begenerated. Although the disclosure focus is on subsurface opticalstructures, disclosure contemplates any suitable optical structures, forexample, optical structures that are not subsurface.

FIG. 10 illustrates an example method 1000 for determining parametersfor forming a subsurface optical structure for improving vision in apatient. The method may include, at step 1010, accessing a first opticalprescription for the patient, wherein the first optical prescriptioncomprises one or more prescription parameters for refracting lightdirected at a retina of the patient so as to improve vision. At step1020, the method may include generating a first variable wavefront basedon the first optical prescription, wherein the first variable wavefrontcomprises at least one portion that has a phase height greater than 1wave. At step 1030, the method may include phase wrapping the firstvariable wavefront, wherein phase wrapping the first variable wavefrontcomprises collapsing the first variable wavefront to a firstphase-wrapped wavefront having a first predetermined phase height. Atstep 1040, the method may include generating, based on the firstphase-wrapped wavefront, energy output parameters for forming a firstsubsurface optical structure in an ophthalmic lens using an energysource, wherein the first subsurface optical structure is configured torefract light directed at the retina of the patient so as to improvevision.

Particular embodiments may repeat one or more steps of the method ofFIG. 10 , where appropriate. Although this disclosure describes andillustrates particular steps of the method of FIG. 10 as occurring in aparticular order, this disclosure contemplates any suitable steps of themethod of FIG. 10 occurring in any suitable order. Moreover, althoughthis disclosure describes and illustrates an example method fordetermining parameters for forming a subsurface optical structure forimproving vision in a patient, including the particular steps of themethod of FIG. 10 , this disclosure contemplates any suitable method fordetermining parameters for forming a subsurface optical structure forimproving vision in a patient, including any suitable steps, which mayinclude all, some, or none of the steps of the method of FIG. 10 , whereappropriate. Furthermore, although this disclosure describes andillustrates particular components, devices, or systems carrying outparticular steps of the method of FIG. 10 , this disclosure contemplatesany suitable combination of any suitable components, devices, or systemscarrying out any suitable steps of the method of FIG. 10 .

FIG. 11 illustrates an example of presbyopia progression in a patient.In order to focus on objects near to the eye, the natural lens of theeye (e.g., the human crystalline lens) needs to be able to accommodate,or change its shape to appropriately focus the convergence of light rayson the retina from the object. This is accomplished by contraction ofthe ciliary muscles coupled to the lens. As a patient ages, the naturallens tends to stiffen (a reduction in elasticity) and/or grow in size(axial and/or equatorial growth) with age, making it increasinglydifficult for the ciliary muscle to cause the lens to accommodateappropriately. As a result, the patient may experience a reduction inthe ability to focus on near or intermediate objects. This condition maybe termed presbyopia, and an example progression is illustrated in FIG.11 , which shows the amplitude of accommodation possible with apatient's natural lens as a function of age. A diopter may be defined as1/d, where d is an distance between the eye and an object in meters. Asillustrated, the patient may have a relatively high amplitude ofaccommodation at age 10, being able to appropriately accommodate forobjects as near as around 1/13 or 1/14 meters away from the eye (i.e.,13 or 14 diopters). As the patient ages, this amplitude of accommodationgradually begins to decrease. At around the age of 40, presbyopiatypically begins to be noticeable. In the example of FIG. 11 , at aroundthe age of 40, the patient may be unable to appropriately accommodatefor objects farther than ¼ meters away. Generally, patients less than 45years old may be classified as early presbyopes requiring relativelyminor correction. Presbyopia patients between 45 and 55 years old may beclassified as mid presbyopes requiring a moderate level of correction.Referencing FIG. 11 , the presbyopia in the patient during this agerange may have progressed such that the patient is unable toappropriately accommodate for objects farther than ½ meters away.Presbyopia patients over the age of 55 years old (or patients who havereceived a non-accommodating intraocular lens) may be classified asadvanced presbyopes requiring a relatively large level of correction.Referencing FIG. 11 , the presbyopia in the patient after 55 years mayhave progressed such that the patient can no longer accommodate forobjects closer than 1 meter away.

FIG. 12 illustrates an example chart of presbyopia progression. FIG. 12shows typical accommodating ability for early presbyopes, midpresbyopes, and advanced presbyopes (or those with a monofocalnon-accommodating IOL). FIG. 12 also shows appropriate add powers thatmay be needed to improve near and/or intermediate vision for eachrespective stage of presbyopia progression. For example, an earlypresbyope may need 1 diopter of add power, a mid presbyope may need 2diopters of add power, and an advanced presbyope may need 3 diopters ofadd power. These add powers may be provided by, for example, providingoptical structures (e.g., subsurface optical structures within anophthalmic lens) that implement an appropriate wavefront capable ofdiffracting light so as to refocus light rays coming from an object.

FIG. 13 illustrates example image quality metrics across a diopter rangeusing a number of bifocal wavefronts. Referencing FIG. 13 , the line1310 illustrates an example of image quality as a function of defocus(in units of diopters) for a patient with presbyopia. The patient hasrelatively high image quality at low diopters corresponding to farvision (e.g., an image-quality value of around 0.9 at 0 diopters wherean object is infinitely far away) and relatively low image quality athigh diopters corresponding to near vision (e.g., an image-quality valueof around 0.2 at 2 diopters where an object is 0.5 meters away). Theimage quality metrics shown in FIG. 13 (and similarly in FIGS. 15, 16,17, and 18 ) are known as the “image convolution metric,” which numerousstudies have shown to be an excellent proxy for high contrast visualacuity. More information about such metrics may be found in thefollowing references, which are incorporated herein in their entiretyfor all purposes: Watson, Andrew B. et al., “Predicting visual acuityfrom wavefront aberrations.” Journal of Vision 8.4 (2008): 17-17;Zheleznyak, Len et al., “Modified monovision with spherical aberrationto improve presbyopia through-focus visual performance,” InvestigativeOphthalmology & Visual Science 54.5 (2013): 3157-3165; Zheleznyak, Lenet al., “Impact of pupil transmission apodization on presbyopiathrough-focus visual performance with spherical aberration,”Investigative Ophthalmology & Visual Science 55.1 (2014): 70-77; andKim, Myoung Joon, et al., “Improving Through-Focus Visual PerformanceUsing Primary And Secondary Spherical Aberrations,” InvestigativeOphthalmology & Visual Science 53.14 (2012): 6332-6332.

The typical way of improving near vision in patients with presbyopia iscausing light to diffract to multiple focal points using an opticalelement. For example, a bifocal contact lens, a bifocal IOL, or a corneamodification may be used to focus light rays from objects at two focalpoints—e.g., a first focal point for nearby objects and a second focalpoint for far objects. Referencing FIG. 13 , the line 1320 correspondsto a conventional bifocal lens with a 2-diopter add power. Asillustrated, the bifocal lens diffract slate so as to create two peaksof high image quality—the first peak at 0 diopters and the second peakat around 2 diopters—corresponding to the two focal points of thebifocal. This typically results in an overall improvement of vision byallowing the patient to see relatively well around the two peaks, but itis nonetheless suboptimal because there is a large range in between thepeaks (intermediate vision) where image quality drops off significantly.

In some embodiments, the range in between the peaks can be shortenedusing an ophthalmic lens with a lower diopter value. For example, a1.5-diopter bifocal may be used instead of a 2-diopter bifocal. Doing soshifts the image-quality peak toward better intermediate vision ascompared to an ophthalmic lens with a higher diopter value, but reducesimage quality for a range of near vision. In some embodiments, theophthalmic lens may be made to correspond to a wavefront generated usingthe phase-wrapping process described previously. That is, the wavefrontof a typical bifocal may be collapsed to a predetermined phase heightthat is less than 1 wave. For example, referencing FIG. 13 , the lines1330 and 1340 correspond to 1.5-diopter bifocal with a wavefront thathas been collapsed to 0.4 waves and 0.5 waves respectively. Asillustrated, phase-wrapping the wavefront adjusts the curvature of theimage-quality line. An optimal phase height and an optimal add power ofthe lens may be determined based on the “visual diet” of the patient,e.g., which may correspond to the relative percentages of time thepatient focuses at each distance on an average day. As is evident fromthese lines, implementing diffractive wavefronts generally involvessignificant trade-offs among near, intermediate, and far vision. Thatis, these diffractive wavefronts on their own are typically unable tocreate optimal vision across the entire range of a patient's vision fromnear vision to far vision. For example, while the lines 1330 and 1340corresponding to the phase-wrapped wavefronts may be an improvement overthe line 1320 corresponding to the conventional bifocal, they still havean intermediate-vision range in between their respective peaks thatprovides suboptimal image quality.

FIG. 14 illustrates the concept of spherical aberrations in lenses.Typically, all spherical lenses have some degree of sphericalaberration. As illustrated in FIG. 14 , a lens 1410 with zero sphericalaberration focuses all incoming rays of light at a single focal point.In some embodiments, an ophthalmic lens may be made to deliberatelyintroduce a spherical aberration in order to refocus light to helpcorrect presbyopia. There may be two general types of sphericalaberrations: negative spherical aberrations and positive sphericalaberrations. Negative spherical aberrations cause peripheral rays (rayscloser to the periphery of the lens 1420) passing through the lens 1420to be refracted by a smaller amount than central rays (rays closer tothe center, or optical axis, of the lens 1420). Thus, as illustrated inFIG. 14 , the more central rays passing through the lens 1420 come to afocal point prior to the more peripheral rays. Positive sphericalaberrations cause the peripheral rays passing through the lens 1430 tobe refracted by a larger amount than the central rays. Thus, asillustrated in FIG. 14 , the more peripheral rays passing through thelens 1430 come to a focal point prior to the more central rays.

FIG. 15 illustrates example image quality metrics for a patient withpresbyopia with lenses having positive and negative sphericalaberrations as compared to a control with zero spherical aberration.Introducing spherical aberrations (both positive and negative) maygenerally decrease image quality for far vision as compared to thecontrol, but may increase image quality for near and intermediatevision. For example, referencing FIG. 15 , the lines 1520 and 1530corresponding to positive and negative spherical aberrations,respectively, produce a decrease in image quality at the extreme of farvision (e.g., at 0 diopters) as compared to the control 1510, and anincrease in image quality at more intermediate and near ranges (e.g.,after about 0.4 diopters) as compared to the control 1510. As is evidentfrom FIG. 15 , positive and negative spherical aberrations have theirown trade-offs (e.g., with positive spherical aberrations as illustratedby the line 1520 producing better intermediate vision but worse nearvision than negative spherical aberrations as illustrated by the line1530). As FIG. 15 illustrates, although spherical aberrations can beused to provide an improvement over a control with zero aberrations,they are overall limited in their capability for providing an extendedrange of high image quality from near to far vision. That is, while theyprovide some gains in far vision, there is a drop-off when it comes tonear and/or intermediate vision.

FIG. 16 illustrates a graph overlaying the line 1320 for a 2-diopterbifocal of FIG. 13 with the spherical aberration lines 1520, 1530 andthe control line 1510 of FIG. 15 . As can be seen in the example of FIG.16 , the image quality metrics of the bifocal line 1320 (e.g., at andaround the 2-diopter peak) provide an improvement to the drop-off innear and/or intermediate vision that occurs on the spherical aberrationlines 1520, 1530. And the image quality metrics of the sphericalaberration lines 1520, 1530 provide an improvement to the valley betweenthe peaks of the bifocal line 1320 (e.g., between about zero and 2diopters). Thus, there are qualities for both spherical aberrations andmultifocals (e.g., bifocals) that may be complementary to each other.Embodiments of the disclosure attempt to create a lens corresponding toa unified wavefront that merges both qualities together, as will beexplained below.

FIG. 17 illustrates the graph of FIG. 16 further overlaying linescorresponding to image quality metrics of phase-wrapped trifocals. Thelines 1710 and 1720 both correspond to trifocals centered at 1 diopterand 2 diopters, but the line 1710 corresponds to a trifocal phasewrapped at 0.6 waves and the line 1720 corresponds to a trifocal phasewrapped at 0.5 waves. As illustrated, the trifocals provide animprovement over the bifocal corresponding to the line 1610 over therange between 0 and 2 diopters. For example, the trifocals provide anadditional peak at 1 diopter and generally reduce drop-offs in imagequality between their peaks (i.e., in the illustrated example, betweenthe peaks at 0 and 1 diopter and between the peaks at 1 and 2 diopters)due to their respective phase wrapping. However, the drop-offs betweenpeaks may not allow for consistent image quality, which may beperceptible to the patient, and as such may still not be ideal inproviding a seamless extended range of vision.

FIG. 18A illustrates a graph including a number of the previouslydescribed lines as well as lines 1810, 1820 corresponding phase-wrappedwavefronts (at 0.5 waves) including both defocus (of 1.5 diopters and2.0 diopters, respectively) and spherical aberration. The line 1810corresponds to a 1.5-diopter bifocal with a −0.2 μm sphericalaberration. The line 1820 corresponds to a 2-diopter bifocal with a −0.2μm spherical aberration. As shown in FIG. 18 , the lines 1810 and 1820provide image quality that is generally high and consistent across alarge range of vision. For example, the line 1810 provides relativelyhigh image quality up to around 2 diopters, with image quality for alarge portion of this range being relatively constant. Similarly, theline 1820 provides high image quality up to about 2.5 diopters, againremaining relatively constant for much of this range (but with a slightdip). By contrast, the other lines all exhibit sharp drop-offs in imagequality at one or more points along this range.

FIGS. 19A-19B illustrate cross-sections of the wavefronts correspondingto the lines 1810 and 1820 of FIG. 18 . FIG. 19A corresponds to the line1810 (1.5-diopter bifocal with a −0.2 μm spherical aberration) and FIG.19B corresponds to the line 1820 (2-diopter bifocal with a −0.2 μmspherical aberration). As shown, these wavefronts have beenphase-wrapped to have a phase height of 0.5 waves.

In some embodiments, the wavefronts may be phase wrapped as describedpreviously. Any suitable phase height may be predetermined for the phasewrapping. In some embodiments, the phase height may be less than 1 wave.For example, a wavefront may be phase wrapped to 0.5 waves or 0.6 waves.As previously discussed, the phase height chosen for phase wrappingaffects how light energy is distributed between near, intermediate, andfar vision. For example, referencing the example graph in FIG. 7 , at aphase height of 0.5 waves, light is equally distributed between near andfar vision. As phase height is increased toward 1 wave, more of thelight is distributed toward near vision than toward far vision. Bycontrast, as phase height is decreased toward 0 waves, more of the lightis distributed toward far vision than toward near vision. A suitablephase height may be determined for the patient based on, for example,the “visual diet” of the patient as explained previously.

FIG. 20 is a table showing example wavefronts that may be implementedfor different stages of presbyopia. As previously explained, presbyopiatypically progresses with age, and patients can be characterized broadlyas early presbyopes, mid presbyopes, and advanced presbyopes. Aspreviously expressed, any suitable wavefront may be implemented by thedescribed system to form a necessary ophthalmic lens. Some examplewavefront characteristics for each stage are noted in FIG. 20 . Using anenergy source (e.g., a laser), optical structures may be formed in anophthalmic lens (e.g., subsurface optical structures within theophthalmic lens) to implement any suitable wavefront so as to correct apatient's vision as desired.

In some embodiments, these implementations may be phased in aspresbyopia progresses. For example, an early presbyope patient may betreated with an ophthalmic lens implementing a wavefront suitable forearly presbyopes. The same patient may later get a further treatmentsuitable for a mid presbyope once the patient's presbyopia hasprogressed to that stage. Similarly, the same patient may later get afurther treatment suitably for an advanced presbyope once the patient'spresbyopia has progressed to that stage. The systems and methodsdescribed herein are advantageous in that they allow this phasing inapproach even in corneal or IOL ophthalmic lenses. For example, apatient with an IOL for early presbyopia can get a further treatment formid or advanced presbyopia without needing a new IOL implant surgery.Instead, an energy system (e.g., a laser system) can simply modify therefractive index of the IOL as needed to implement a suitable wavefront.

FIG. 21 illustrates an example method 2100 for generating parameters forforming a subsurface optical structure in an ophthalmic lens forcorrecting presbyopia in a patient. The method may include, at step2110, generating a first phase-wrapped wavefront corresponding to afirst optical structure configured to cause the ophthalmic lens todiffract light to multiple focal points, wherein the first phase-wrappedwavefront is a wavefront having a first predetermined phase height lessthan 1 wave. The first phase-wrapped wavefront may be generated based onan optical prescription for the patient, where the optical prescriptionincludes one or more prescription parameters for refracting lightdirected at a retina of the patient so as to improve vision. From thisoptical prescription, a first variable wavefront may be generated,wherein the first variable wavefront comprises at least one portion thathas a phase height greater than 1 wave. This variable wavefront may thenbe collapsed to the first predetermined phase height to generate thefirst phase-wrapped wavefront. At step 2120, the method may includegenerating a first spherical wavefront configured to cause a firstspherical aberration in the ophthalmic lens. The first sphericalwavefront may also be based on the first optical prescription, and maybe generated based on simulations of image quality metrics that wouldresult from combining the first spherical wavefront with the firstphase-wrapped wavefront. Optimal spherical and phase-wrapped wavefrontsmay be determined based on the simulations, in light of the patient'slifestyle or “visual diet” as explained above. At step 2130, the methodmay include generating, based on the first phase-wrapped wavefront andthe first spherical wavefront, energy output parameters for forming afirst subsurface optical structure in the ophthalmic lens using anenergy source, wherein the first subsurface optical structure isconfigured to correct presbyopia with an extended depth of focus thatallows for increased intermediate vision quality.

Particular embodiments may repeat one or more steps of the method ofFIG. 21 , where appropriate. Although this disclosure describes andillustrates particular steps of the method of FIG. 21 as occurring in aparticular order, this disclosure contemplates any suitable steps of themethod of FIG. 21 occurring in any suitable order. Moreover, althoughthis disclosure describes and illustrates an example method forgenerating parameters for forming a subsurface optical structure in anophthalmic lens for correcting presbyopia in a patient, including theparticular steps of the method of FIG. 21 , this disclosure contemplatesany suitable method for generating parameters for forming a subsurfaceoptical structure in an ophthalmic lens for correcting presbyopia in apatient, including any suitable steps, which may include all, some, ornone of the steps of the method of FIG. 21 , where appropriate.Furthermore, although this disclosure describes and illustratesparticular components, devices, or systems carrying out particular stepsof the method of FIG. 21 , this disclosure contemplates any suitablecombination of any suitable components, devices, or systems carrying outany suitable steps of the method of FIG. 21 .

Adjusting for Implementation Limitations

A design phase-wrapped wavefront, as an abstract construct, can havevertical steps with infinitely abrupt changes in wavefront slope asdescribed herein. Implementation of the design phase-wrapped wavefrontin an artificial or biological optical material, however, can result indifferences between the resulting optical correction and the opticalcorrection corresponding to the design phase-wrapped wavefront. Theresulting optical differences can result from what is referred to hereinas a low-pass filtering of the design phase-wrapped wavefront. Thelow-pass filtering of the design phase-wrapped wavefront can have manycauses including, but not limited to, the size of the laser point spreadfunction, the volumes of the laser induced refractive index changes(LIRIC) in the artificial or biological optical material, and/orpost-LIRIC changes in the artificial or biological optical material(e.g., biological remodeling, swelling, etc.).

To assess the impact of the low-pass filtering, simulation ofthrough-focus retinal image quality (RIQ) (monochromatic at 550 nm, 3 mmpupil diameter, 3 diopter add-power diffractive multifocal wavefront,Image Convolution Metric) was simulated using Matlab for differentamounts of low-pass filtering with a Gaussian function (full width athalf maximum (FWHM) from 2 um to 188 um). FIG. 22 illustrates simulatedresulting phase-wrapped wavefronts 2210, 2220, 2230, 2240, 2250, 2260,2270 for an intended 0.4 wave height phase-wrapped wavefront due to theimpact of the different amounts of the low-pass filtering. Asillustrated, the peak wave heights of the resulting effectivephase-wrapped wavefront are increasingly reduced in magnitude from thedesign 0.4 wave height for increasing magnitudes of the low-passfiltering. FIG. 23 illustrates simulated resulting through-focus (RIQ)2310, 2320, 2330, 2340, 2350, 2360, 2370 for the simulated resultingphase-wrapped wavefronts of FIG. 22 . The simulated resultingthrough-focus RIQs show increasing reduction in near visual benefit andnear vision RIQ, and increases distance RIQ for increasing magnitudes ofthe low-pass filtering, ultimately reverting to the pre-treatment RIQ atthe highest magnitude of the low-pass filtering.

To compensate for the impact of the low-pass filtering on thethrough-focus (RIQ), the design peak wave height can be increased orscaled by a suitable amount. For example, FIG. 24 illustrates simulatedresulting phase-wrapped wavefronts 2410, 2420, 2430, 2440, 2450, 2460,2470 for a scaled-up version of the design 0.4 wave height phase-wrappedwavefront of FIG. 22 . The scaled-up version of the design 0.4 waveheight phase-wrapped wavefront has been scaled up by (1.0/0.4) toincrease the wavefront peaks from 0.4 wave to 1.0 wave. FIG. 24illustrates simulated resulting phase-wrapped wavefronts for thescaled-up version of the design 0.4 wave height phase-wrapped wavefrontdue to the impact of the different amounts of the low-pass filtering. Asillustrated, the peak wave heights of the resulting effectivephase-wrapped wavefront are increasingly reduced in magnitude from theresulting 1.0 wave height for increasing magnitudes of the low-passfiltering. FIG. 25 illustrates simulated resulting through-focus (RIQ)2510, 2520, 2530, 2540, 2550, 2560, 2570 for the simulated resultingphase-wrapped wavefronts of FIG. 24 . The simulated resultingthrough-focus RIQs for the scaled-up version show increased near visualbenefit and near RIQ relative to the design 0.4 wave heightphase-wrapped wavefront for the different amounts of the low-passfiltering. FIG. 26 shows simulated resulting through-focus retinal imagequalities illustrating that near visual benefit can be recovered byscaling the design wavefront height. As illustrated, the scaled-upversion of the design 0.4 wave height phase-wrapped wavefront has acomparable through focus RIQ 2620 at a higher level of low-passfiltering (94 um FMHM) relative to the design 0.4 wave heightphase-wrapped wavefront 2610 at a lower level of low-pass filtering (2um FWHM). Accordingly, scaling up of a design phase-wrapped wavefrontcan be used to compensate for the impact of resulting low-pass filteringassociated with physically inducing the phase-wrapped wavefront in anartificial or biological optical material.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A method for generating parameters for forming asubsurface optical structure in an ophthalmic lens for correctingpresbyopia in a patient, the method comprising: defining a firstphase-wrapped wavefront corresponding to a first optical structureconfigured to cause an ophthalmic lens to diffract light to multiplefocal points, wherein the first phase-wrapped wavefront is a wavefronthaving a first predetermined phase height; defining a first sphericalwavefront configured for inducing a first spherical aberration in theophthalmic lens; and generating, based on the first phase-wrappedwavefront and the first spherical wavefront, energy output parametersfor forming a first subsurface optical structure in the ophthalmic lensusing an energy source, wherein the first subsurface optical structureis configured to correct presbyopia by providing an extended depth offocus that produces increased intermediate vision quality.
 2. The methodof claim 1, wherein the first predetermined phase height is not equal to1 wave.
 3. The method of claim 1, further comprising: accessing anoptical prescription for the patient, wherein the optical prescriptioncomprises one or more prescription parameters for refracting lightdirected at a retina of the patient so as to improve vision; anddefining a first variable wavefront based on the optical prescription,wherein the first variable wavefront comprises at least one portion thathas a phase height greater than 1 wave; wherein defining the firstphase-wrapped wavefront comprises collapsing the first variablewavefront to the first predetermined phase height.
 4. The method ofclaim 1, wherein the energy output parameters specify a plurality ofpower levels corresponding to a plurality of optical zones on theophthalmic lens, the method further comprising: directing a first energybeam from the energy source at a first subsurface optical zone of theophthalmic lens for a first duration, wherein a power level of the firstenergy beam is based on a corresponding power level as specified by theenergy output parameters; and directing a second energy beam from theenergy source at a second subsurface optical zone of the ophthalmic lensfor a second duration, wherein a power level of the second energy beamis based on a corresponding power level as specified by the energyoutput parameters; wherein the first energy beam and the second energybeam alter refractive indexes of the first subsurface optical zone andthe second subsurface optical zone, respectively, and wherein the firstsubsurface optical structure comprises the first subsurface optical zoneand the second subsurface optical zone.
 5. The method of claim 1,wherein the first optical structure is configured to cause theophthalmic lens to be a bifocal lens having a 2 diopter add power. 6.The method of claim 1, wherein the first optical structure is configuredto cause the ophthalmic lens to be a bifocal lens having a 1.5 diopteradd power.
 7. The method of claim 1, wherein the first predeterminedphase height is between about 0.5 to 0.6 waves.
 8. The method of claim7, wherein the first spherical aberration is around −0.2 μm.
 9. Themethod of claim 7, wherein the first spherical aberration is around 0.2μm.
 10. The method of claim 1, wherein forming the subsurface opticalstructure comprises directing an energy beam toward a volume of theophthalmic lens so as to change a refractive index of the volume. 11.The method of claim 1, further comprising: defining a secondphase-wrapped wavefront corresponding to a second optical structureconfigured to cause the ophthalmic lens to diffract light to multiplefocal points, wherein the second phase-wrapped wavefront is a wavefronthaving a second predetermined phase height; defining a second sphericalwavefront configured for inducing a second spherical aberration in theophthalmic lens; and generating, based on the second phase-wrappedwavefront and the second spherical wavefront, energy output parametersfor forming a second subsurface optical structure in the ophthalmic lensusing an energy source.
 12. The method of claim 11, wherein the secondpredetermined phase height is not equal to 1 wave.
 13. The method ofclaim 11, wherein the first subsurface optical structure is configuredto correct a first stage of presbyopia in the patient, and wherein thesecond subsurface optical structure is configured to correct a secondstage of presbyopia in the patient, wherein the second stage ofpresbyopia in the patient occurs after the first stage of presbyopia inthe patient.
 14. An ophthalmic lens for correcting presbyopia in apatient, the ophthalmic lens comprising: a first subsurface opticalstructure comprising concentric Fresnel rings within an interior of theophthalmic lens, each of the concentric Fresnel rings defining a volumehaving a desired refractive index, wherein the first subsurface opticalstructure is configured to: cause a first spherical aberration in theophthalmic lens; and diffract light to multiple focal points based on aphase-wrapped wavefront having a first predetermined phase height notequal to 1 wave.
 15. The ophthalmic lens of claim 14, wherein theophthalmic lens is an intraocular lens, a contact lens, or a cornea ofthe patient.
 16. The ophthalmic lens of claim 14, wherein the firstsubsurface optical structure is configured to cause the ophthalmic lensto be a bifocal lens having a 2 diopter add power.
 17. The ophthalmiclens of claim 14, wherein the first subsurface optical structure isconfigured to cause the ophthalmic lens to be a bifocal lens having a1.5 diopter add power.
 18. The ophthalmic lens of claim 14, wherein thefirst predetermined phase height is between about 0.5 to 0.6 waves. 19.The ophthalmic lens of claim 18, wherein the first spherical aberrationis around −0.2 μm.
 20. The ophthalmic lens of claim 18, wherein thefirst spherical aberration is around 0.2 μm.
 21. The ophthalmic lens ofclaim 14, wherein the ophthalmic lens further comprises a secondsubsurface optical structure, wherein the first subsurface opticalstructure is embedded in a first layer of the ophthalmic lens and thesecond subsurface optical structure is embedded in a second layer of theophthalmic lens.
 22. The ophthalmic lens of claim 21, wherein the firstsubsurface optical structure is configured to correct a first stage ofpresbyopia in the patient, and wherein the second subsurface opticalstructure is configured to correct a second stage of presbyopia in thepatient, wherein the second stage of presbyopia in the patient occursafter the first stage of presbyopia in the patient.